How to get the build variant at runtime in Android Studio?

I'd like to get the build variant during runtime, is this possible without any extra config or code?

Look at the generated BuildConfig class.

public final class BuildConfig {
  public static final boolean DEBUG = Boolean.parseBoolean("true");
  public static final String APPLICATION_ID = "com.example.app";
  public static final String BUILD_TYPE = "debug";
  public static final String FLAVOR = "";
  public static final int VERSION_CODE = 1;
  public static final String VERSION_NAME = "";
}

Another option would be to create a separate build config variable for each build variant and use it in your code like this:

In your build.gradle file:

productFlavors {

    production {
        buildConfigField "String", "BUILD_VARIANT", "\"prod\""
    }

    dev {
        buildConfigField "String", "BUILD_VARIANT", "\"dev\""
    }       
}

To use it in your code:

if (BuildConfig.BUILD_VARIANT.equals("prod")){ // do something cool }

Here is an example to define and get BuildConfig for different flavor

android {

    defaultConfig {
        ...
    buildTypes {
        ...
    }

    flavorDimensions "default"
    productFlavors {

        develop {
            applicationIdSuffix ".dev"
            versionNameSuffix "-dev"
        }

        staging {
            applicationIdSuffix ".stg"
            versionNameSuffix "-stg"
        }

        production {
            applicationIdSuffix ""
            versionNameSuffix ""
        }
    }

    applicationVariants.all { variant ->

        def BASE_URL = ""

        if (variant.getName().contains("develop")) {
            BASE_URL = "https://localhost:8080.com/"
        } else if (variant.getName().contains("staging")) {
            BASE_URL = "https://stagingdomain.com/"
        } else if (variant.getName().contains("production")) {
            BASE_URL = "https://productdomain.com/"
        }
        variant.buildConfigField "String", "BASE_URL", "\"${BASE_URL}\""

    }
}

Using

BuildConfig.BASE_URL

You can try with

getPackageName(); 

it will return what you've defined in build.gradle

productFlavours{
  flavour1{
     applicationId 'com.example.package.flavour1'
  }
  flavour2{
     applicationId 'com.example.package.flavour2'
  }
}